Genetic and biochemical abnormalities of alpha-synuclein are directly implicated in the pathogenesis of Parkinson's disease (PD) and other alpha-synucleinopathies. Transgenic (Tg) A53T mutant alpha-synuclein mice develop adult-onset disease with a progressive motoric dysfunction leading to death. The affected mice exhibit many of the feaures of human alpha-synucleinopathies including neuronal accumulations of alpha-synuclein and ubiquitin in many neuronal populations and increased insolubility and biochemical alterations of alpha-synuclein. We propose the following aims to more fully define mechanisms of alpha-synuclein dependent in vivo degeneration of neuronal populations. 1. To characterize the temporal and spatial changes in the neurodegeneration associated cellular processes in Hu alpha-synuclein Tg mice. The mechanisms leading to neuronal dysfunction and death in alpha-synucleinopathies are not known. By detailed pathological analysis of alpha-synuclein Tg mice, we will determine potential cellular processes that are involved in alpha-synucleinopathy associated neurondegeneration in vivo. 2. To characterize human alpha-synuclein metabolism, truncation, phosphorylation as a function of neuronal cell types, aging, and alpha-synucleinopathy in mice. Changes in cellular metabolism and posttranslational modifications may by a significant factor in alpha-synucleinopathies. We will examine whether cell types, aging and disease states are associated with alpha-synuclein metabolism that promote alpha-synucleinopathies. 3. To characterize Hu alpha-synuclein metabolism, truncation, and aggregation as a function of neuronal cell type, aging, and disease in human brain. We will examine whether regional variations in alpha-synuclein metabolism/posttranslational modifications are associated with increased in human alpha-synucleinopathies. We will also determine whether alpha-synucleinopathies in humans are associated with alterations in metabolism, truncations, and aggregation of alpha-synuclein. 4. To determine whether alpha-synuclein metabolism and truncation is affected by Ser-129 phosphorylation, Synphilin, Parkin, and DJ-1. In collaboration with Projects 1, 2, and 4, this aim will examine whether other PD related processes and genes directly affect alpha-synuclein metabolism and truncation. 5. To determine whether the C-terminal truncations of Hu alpha-synuclein increases toxicity and aggregation of Hu alpha-synuclein in cultured cells and in transgenic mice. In conjunction with Drs. Chris Ross (Project 2) and Valina Dawson (Project 4), we will establish that C-terminally truncated alpha-synucleins shows enhanced toxicity and aggregation properties in cultured cells (SH-SY5Y, PC-12 and primary mesencephalic neurons). To establish the pathogenic importance in vivo, we will analyze Tg mice expressing truncated human alpha-synuclein (generated in Transgenic Core).